Kidney transplantation surgery is an accepted form of therapy for patients with end stage renal disease, and over 8,000 surgeries are performed each year in the USA. Lack of donor organs, rejection, and preservation/reperfusion injury are the main obstacles to overcome in kidney transplantation. Preservation reperfusion injury leads to delayed graft function (DGF) requiring postoperative hemodialysis which adds additional cost to the procedure and results in reduced long-term survival of kidneys (5 to 10 years). During our previous period of support we developed a new preservation solution (one for cold storage and one for machine perfusion) for the kidney and other organs. These solutions improved dramatically the quality and duration of kidney (and other organ) preservation. We identified some of the problems with kidney preservation including microvascular injury as well as renal tubular injury related to calcium and possibly phospholipid (arachidonic acid) metabolism. Our underlying hypothesis in this proposal is that microvascular injury may be a primary cause of renal injury upon reperfusion. Our overall goal is to understand the cellular and biochemical mechanisms underlying preservation/reperfusion injury to the kidney and to develop more effective preservation methods. Our specific aims are: l) to understand changes in the microvascular system of the preserved kidney using blood and erythrocyte models of the isolated perfused rabbit kidney; 2) to understand the relationship between phospholipid metabolism (hydrolysis and reacylation) and eicosanoid production and microvascular and tubular changes during preservation or reperfusion; 3) to understand how endothelial cells and tubular cells are injured by hypothermic preservation and reperfusion using isolated endothelial and tubular cells; 4) to study how various agents and drugs affect the quality of preservation of rabbit organs and isolated cells as related to proposed mechanisms of injury; 5) to use the clinically relevant dog kidney autotransplant model to test new and improved methods of kidney preservation derived from specific aims 1-4. These studies will provide new and useful information for understanding the pathogenesis of delayed graft function in the kidney. The new information generated will lead to better renal preservation, reduced cost, and better long-term graft survival in human kidney transplantation therapy.